In a controlled object, a process variable of a controlled object process is detected by a sensor and its detection time is measured by a timer. A process signal transmitting device transmits, as a process signal, the process variable and the detection time to a control apparatus. A control variable calculating device calculates a control variable based on the received process variable and a control reference value, and transmits a control signal including the control variable and the received process variable detection time to the controlled object. In the controlled object, a control signal receiving device calculates a transmission delay, that is, a difference between control signal reception time that is measured by the timer and the transmitted process variable detection time, corrects the control variable by processing it in accordance with the transmission delay, and drives an actuator by using the corrected control variable.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A network control system for transmitting signal between a control apparatus and a controlled object, said control apparatus comprising: a process signal receiving device for receiving a process signal outputted from the controlled object, the process signal includes a time information related to an observed process variable; a control variable calculating device for calculating a control variable for a process in the controlled object based on the process signal; and, a control signal outputting device for outputting a control signal including the calculated control variable and a detection time of the process variable to the controlled object; and said controlled object comprising: a control signal inputting device for receiving the control signal that is outputted from said control apparatus; a driver for driving a process of said controlled object based on the control variable included in the control signal; a detector for detecting the process variable of the process thus driven; a time measuring device for measuring a detection time of the process variable and reception time of the control signal; and a process signal outputting device for outputting the process signal including the detected process variable and the measured process variable detection time to said control apparatus, wherein said control signal inputting device further calculates a transmission delay that is a difference between the control signal reception time and the process variable detection time that is included in the control signal, corrects the control variable by processing in accordance with the transmission delay, and outputs a corrected control variable to said driver.
2. The network control system according to claim 1, wherein the control variable calculating device sets a plurality of assumed transmission delays and calculates optimum control variables for the respective assumed transmission delays, said control signal outputting device outputs the calculated control variables en bloc as the control signal, and said control signal receiving device selects one of the control variables included in the control signal corresponding to an assumed transmission delay that is closest to an actual transmission delay, and outputs a selected control variable to the driver as the corrected control variable.
3. The network control system according to claim 1, wherein said control variable calculating device calculates an optimum control variable response locus for a predetermined period from a present time, said control signal outputting device outputs the optimum control variable response locus in such a manner that it is included in the control signal, and said control signal inputting device stores the optimum control variable response locus included in the received control signal, and sequentially outputs, to said driver, values of the optimum control variable response locus as the corrected control variables in accordance with time that is measured by said time measuring device until reception of a next control signal.
4. The network control system according to claim 3, wherein the process signal outputting device combines a preceding control variable and preceding control signal reception time with the process variable and the process variable reception time to generate the process signal, and wherein the control variable calculating device comprises: a model holding section for holding a model of said controlled object process and a network model in which a transmission delay is assumed; a data buffer for storing process variable history data of past process variables and a process variable detection time points up to immediately before a present time and control variable history data of past control variables and control signal reception time points up to a preceding cycle; a prediction calculation section for calculating a future process variable prediction response from the present time based on the models held by said model holding section and the process variable and control variable history data stored in said data buffer; and a control variable optimization section for determining a future optimum control variable response locus from the present time so that the process variable prediction response calculated by said prediction calculation section becomes as close to a preset target response locus as possible, and calculates, every time a new process signal is received, an optimum control variable response locus for a predetermined period from a present time by repeatedly performing calculations relating to the process.
5. The network control system according to claim 4, wherein: a plurality of controlled objects connected to a single control apparatus bidirectionally like a star connection via individual network; said control apparatus comprises process signal inputting device for inputting process signals from the controlled objects, control variable calculating device for calculating control signals for said respective controlled objects, and control signal outputting device for outputting the control signals to said respective control signal inputting device provided in said controlled objects via said networks; said control signal calculating device comprises a prediction calculation section for calculating future process variable prediction responses from a present time based on models of respective processes in the controlled objects, mutual interference models each representing an influence of mutual interference between the processes, models of the asynchronous networks in which a transmission delay is assumed, and history data of past values of a plurality of process variables and a plurality of control variables up to the present time, and a control variable optimization section for determining future optimum control variable response loci from the present time so that the process variable prediction responses become as close to respective specified target response loci as possible, and calculates, every time a new process signal is received, an optimum control variable response locus for a predetermined period from a present time by repeatedly performing calculations relating to the process; and said control signal calculating device further calculates, every time a new process signal of any of the process variables is received, optimum control variable response loci for the respective control variables for a predetermined period from a present time by performing calculations of the above functions, and causes the control signal outputting device to output the optimum control variable response loci to said respective controlled objects.
6. The network control system according to claim 1 or 2, wherein: said controlled object further comprises a transmission delay estimating device for estimating an average or a probability distribution function of past transmission delays up to a present time by measuring and storing the process variable detection time and the control variable reception time, and outputting the average transmission delay or the probability distribution function to the control signal receiving device and the process signal outputting device; said control signal inputting device processes the received control signal by using the average transmission delay or the probability distribution function; and said control variable calculating device calculates the control variable in accordance with the average transmission delay or the probability distribution function that is included in the transmitted process signal.
7. A process management method for managing various processes in a controlled object, comprising the steps of: calculating a control variable for execution of one of the processes in the controlled object in accordance with a control reference value and an actual process variable that was detected previously in the controlled object; generating a control signal including the calculated control variable and process variable detection time that has been transmitted from the controlled object; transmitting the control signal to the controlled object via an asynchronous network; measuring reception time of the control signal in the controlled object; calculating a transmission delay that is a difference between the control signal reception time and the process variable detection time; correcting the control variable included in the control signal in accordance with the calculated transmission delay; driving a driver in accordance with the corrected control variable, to thereby execute the process; detecting a process variable of the process being executed and measuring detection time thereof; and generating a process signal including the detected process variable and the measured process variable detection time, and transmitting the process signal to the control apparatus via said network.
8. A recording medium on which a process management program for managing various processes in a controlled object of an network type control system is recorded, the process management program being for causing a computer to execute the steps of: calculating a control variable for execution of one of the processes in the controlled object in accordance with a control reference value and an actual process variable that was detected previously in the controlled object; generating a control signal including the calculated control variable and process variable detection time that has been transmitted from the controlled object; transmitting the control signal to the controlled object via an asynchronous network; measuring reception time of the control signal in the controlled object; calculating a transmission delay that is a difference between the control signal reception time and the process variable detection time; correcting the control variable included in the control signal in accordance with the calculated transmission delay; driving a driver in accordance with the corrected control variable, to thereby execute the process; detecting a process variable of the process being executed and measuring detection time thereof; and generating a process signal including the detected process variable and the measured process variable detection time, and transmitting the process signal to the control apparatus via the asynchronous network.
9. A network control system in which a controlled object and a control apparatus are connected to each other bidirectionally, wherein: the controlled object comprises a process signal transmitting device, a control signal receiving device, and a timer for measuring transmission time and reception time; the process signal transmitting device has a function of transmitting a process variable observation value and process variable transmission time information together; the control apparatus has a function of transmitting process signal transmission time information and corresponding control signal together; and the control signal receiving device has means for calculating a transmission delay from the process signal transmission time and control signal reception time and processing the control signal based on the calculated transmission delay.
10. The network control system according to claim 9, wherein: the control apparatus has a function of assuming a plurality of transmission delays, calculates optimum control variables for the respective assumed transmission delays, and transmitting the optimum control variables as a multiplexed control signal; and the control signal receiving device selects and uses one of the optimum control variables included in the multiplexed control signal that is most suitable for the calculated transmission delay.
11. The network control system according to claim 9, wherein the control apparatus has a function of calculating a series of future control variables for a predetermined period from a present time and transmitting the series of control variables as a multiplexed control signal, and the control signal receiving device sequentially selects control variables from the series of control variables included in the multiplexed control signal and uses the selected control variables.
12. A network control system for transmitting signal between a control apparatus and a controlled object, comprising: a process signal outputting device connected to said controlled object, for outputting an observed process variable and an output time information; a control signal outputting device connected to said control apparatus, for outputting a control variable taking account of the observed process variable and the output time information; and, a process signal inputting device connected to said controlled object, for calculating delay time of the output time information from said control signal outputting device to said process signal inputting device, and re-calculating the process variable taking account of the calculating delay time.
13. The network control system according to claim 12, wherein said control signal outputting device outputs a plurality of estimated control variables, and said process signal inputting device selects an optimum value from the estimated control variables by consideration of the delay time.
14. The network control system according to claim 12, wherein said control signal outputting device outputs a series of estimated control variables in time order, and said process signal inputting device utilizes the series of estimated control variables until when a new series of estimated control variables is inputted.
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August 20, 1998
June 5, 2001
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